barely audible, this procedure puts you on the right
A geographic coordinate system used by
amateur radio operators and others around the world
is the Maidenhead Locator System (MLS). It is also
commonly referred to as grid locators or grid squares.
The MLS compresses latitude and longitude into a
string of characters to allow position information to
be transmitted with limited precision. This is very
useful when determining distances and angles of
Many web logging sites such as PSKreporter and
WSPR use grid squares. Most data decoding
programs have means to automatically send grid
squares, as well as frequency information, call sign, or
name directly from the program. So, if you are
connected to the Internet and want to provide signal
reports, make sure to enable that feature in the
program, and have your specific grid square and
other information entered properly. To find your
specific grid square, go to www.levinecentral.com/
ham/ grid_square.php and enter your zip code or
city. For example, Chicago has the grid square EN61ev.
CW, RTTY, and BPSK
In my opinion, the best program for receiving CW,
RTTY, and BPSK is Fldigi (Fast and Light Digital Modem
Program). Figure 6 shows Fldigi in action receiving
SITORB. It is a free program developed by radio amateurs.
It handles many other modes as well, and has numerous
features including a built-in spectrum display and audio
filters. You can also enter your frequency, call sign, or
name, and enable automatic reporting to PSKreporter.
Fldigi can be downloaded from www.w1hkj.com
/ Fldigi.html. Check the Internet for frequencies where
these modes can be found. For example, PSK- 31 can be
found at 14.070000 MHz and SITOR at 12.577000 MHz.
WSPR, JT9, and JT65
These modes are used for weak signal
communication. Oftentimes, these signals are so weak
they are not perceptible by ear. These modes are used in
special segments of the ham bands. For example, WSPR
can be found on 14.095600 MHz, and JT65 can be found
on 14.076000 MHz. Note the precision of the dial
settings; see Figure 7 for a JT65 screenshot.
Included with the programs are dial frequencies for all
bands. WSPR has its own website for reporting spots,
while JT9/JT65 uses PSKreporter. These programs can be
found at www.physics.princeton.edu/pulsar/K1JT.
These weak signal modes require coordination of your
PC with Universal Coordinated Time (UTC) to within one
or two seconds. So, make sure to set your computer clock
accordingly, and check it often.
Software for FAX, SSTV,
FAX can also be received with Fldigi. An example of a
noisy weather fax is shown in Figure 8. Fax signals can
often be found around 12.748 and 12.788 MHz. Slow
scan TV signals can be found around 14.230 MHz.
Several programs are available on the Internet for SSTV.
One of the newer picture modes is EasyPal, which
transmits pictures digitally. It can be found at 14.233 MHz.
Perfect pictures can be received if the signal manages to
make it through the noise. Search for it on the Internet.
Hopefully, you have learned a little bit about how to
receive and decode shortwave data signals. It is a very
interesting hobby, and new modes are cropping up all the
time. If you find the subject of decoding radio signals
fascinating, you may want to consider becoming a radio
amateur. Hams are involved with building and studying
receivers, transmitters, and antennas, and experimenting
with the radio modes WSPR, JT65, and BPSK discussed
If you are considering joining the fraternity of radio
amateurs, the ARRL website is the place to start. In the
meantime, have fun with your shortwave radio decoder.
May 2015 61
FIGURE 8. Weather FAX image received with Fldigi.